低温机械碰撞和脉冲放电法制备金属纳米粉末
Metal nanopowder production by cryogenic mechanical collision and pulsed electric discharge methods
摘要：
随着微米和纳米传感器和器件的引入，对纯金属和陶瓷粉末的需求有所增加。球形纯金属粉末及其合金是通过粉末冶金制造路线进行近净成形制造的重要原材料，也是粉末注射成型和增材制造的原料。采用雾化工艺来获得球形粉末可以追溯到20世纪80年代，并且已经开发了不同的态度来保持等离子体电流，包括气体雾化、等离子体雾化、等离子体旋转电极雾化和自由落体雾化。采用上述方法的设施一直是昂贵的。本文提出了两种新的工艺，通过它们可以以相对较低的成本获得纯球形粉末。所提出的第一种方法将通过重合射流（即，低温重合射流或CCJ），而第二种提出的方法涉及由从等离子体通道发射的热引起的金属的熔化和蒸发，所述等离子体通道由金属电极的微米间隔处的电场击穿产生（称为电极-等离子体-雾化方法或EPA）。CCJ方法可能面临挑战，例如由于高速碰撞导致的颗粒冷焊和由于存在高塑性形变和冷加工导致的工艺效率低下，而EPA方法仅需要使用导电材料作为电极。采用EPA法制备了平均粒径为62 nm和300- 400 nm的钛粉。研究还表明，预期CCJ方法生产的钛纳米粉末的污染小于0.05wt%。
英文摘要：
With the introduction of micro and nanosensors and devices, the need for pure metal and ceramic powders have risen. Spherical pure metal powders and their alloys are vital raw materials for near-net-shape fabrication via powder-metallurgy manufacturing routes as well as feed stocks for powder injection molding, and additive manufacturing. Employing atomization processes to achieve spherical powders dates back to 1980s and different attitudes to maintain a plasma current have been developed including gas atomization, plasma atomization, plasma-rotating-electrode atomization, and freefall atomization. Facilities for employing the aforementioned methods have always been expensive. This paper proposes two new processes by which pure spherical powder is achievable with relatively low costs. The first method proposed will deal with attrition of coarse particles in cryogenic milieu via coinciding jets (i.e., cryogenic coinciding jets or CCJ), while the second proposed method concerns melting and evaporation of metals caused by the heat emitted from a plasma channel made by the electric field breakdown at micrometer separations of metallic electrodes (entitled as electrode-plasma-atomization method or EPA). The CCJ method may face challenges such as cold welding of particles due to high speed collision and inefficiency of process because of presence of high plastic deformation and coldworking, whereas the EPA method demands only the use of electrically conductive materials as electrodes. Titanium powder with the particle average sizes of 62nm and also 300-400nm was achieved via the EPA method. Studies also suggest that the CCJ method is expected to produce Titanium nanopowder with less than %0.05wt contamination.
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